The Preliminary Exploration of Micro-Friction Stir Welding Process and Material Flow of Copper and Brass Ultra-Thin Sheets

In the friction stir welding (FSW) of ultra-thin dissimilar metal sheets, different physical material properties, the reduction of plastic metal in the weld zone, and insufficient plastic metal flow lead to poor weld seam shapes and joint qualities. Therefore, it is necessary to study the flow behavior during the FSW of ultrathin sheets. In this study, micro friction stir welding (μFSW) was conducted and analyzed for the butt welding of 0.6-mm-thick ultrathin brass (H62-H) and pure copper (T2-Y) sheets. By analyzing the electric signals of the temperature and force during the welding process, testing the mechanical properties, and analyzing the metallography of the joint, the influences of the process parameters on the metal flow behavior during μFSW were studied. In the proper process conditions, the material preferentially migrated and concentric vortex flow occurred in the vicinity of the shoulder and tool pin action areas. The copper was pushed from the retreating side (RS) to the advancing side (AS) of the weld, allowing it to flow more fully. A mixture of both materials formed at the bottom of the weld nugget, and less migration occurred in the heat-affected zone of the AS at this time. The highest tensile strength can reach 194 MPa, accounting for 82.6% of the copper. The presence of brittle phases Cu5Zn8, AgZn3 and AgZn caused the hardness to fluctuate slightly

K-ion storage enhancement in Sb2O3/reduced graphene oxide using ether-based electrolyte

In this work, an ether-based electrolyte is adopted instead of conventional ester-based electrolyte for an Sb2O3-based anode and its enhancement mechanism is unveiled for K-ion storage. The anode is fabricated by anchoring Sb2O3 onto reduced graphene oxide (Sb2O3-RGO) and it exhibits better electrochemical performance using an ether-based electrolyte than that using a conventional ester-based electrolyte. By optimizing the concentration of the electrolyte, the Sb2O3-RGO composite delivers a reversible specific capacity of 309 mAh g(-1) after 100 cycles at 100 mA g(-1). A high specific capacity of 201 mAh g(-1) still remains after 3300 cycles (111 days) at 500 mA g(-1) with almost no decay, exhibiting a longer cycle life compared with other metallic oxides. In order to further reveal the intrinsic mechanism, the energy changes for K atom migrating from surface into the sublayer of Sb2O3 are explored by density functional theory calculations. According to the result, the battery using the ether-based electrolyte exhibits a lower energy change and migration barrier than those using other electrolytes for K-ion, which is helpful to improve the K-ion storage performance. It is believed that the work can provide deep understanding and new insight to enhance electrochemical performance using ether-based electrolytes for KIBs